Struvite Pyrolysate Recycling for Removing Ammonium from Baker’s Yeast Industry Wastewater

Abstract

Baker’s yeast wastewater contains high concentrations of ammonium (NH₄⁺). In this study, we examined recycling of the struvite pyrolysate for NH₄⁺ removal from Baker’s yeast industry wastewater. Optimum nutrient removal by struvite precipitation was obtained at Mg²⁺/NH₄⁺/PO₄^3- molar ratios of 1.5:1:1 and at pH 9.0. X-ray diffraction (XRD) analysis was conducted on the dry precipitate. It was found that high concentrations Na⁺ and Ca²⁺ present in wastewater affected the pure struvite formation. The pyrolysate of the obtained struvite was performed at a NaOH/NH₄⁺ molar ratios of 1.5:1; a heating temperature 110 ˚C and a time, 3 h. The struvite pyrolysate was recycled repeatedly at pH 9.0. When the recycle times were increased, the NH₄⁺ removal ratio progressively decreased. In a five step process, NH₄⁺ removal was 87.55% in the first cycle and progressively decreased to 30.65% in the fifth cycle. COD removal ratio was gradually decreased with the increase in the number of recycle times. The residual concentration levels of Mg²⁺andNa⁺ in the effluent following struvite reuse cycles was lower than in the effluent following struvite precipitation.